Substring with Concatenation of All Words

You are given a string, s, and a list of words, “words”, that are all of the same length. Find all starting indices of substring(s) in s that is a concatenation of each word in words exactly once and without any intervening characters.

For example, given:

s: "barfoothefoobarman"

words: ["foo","bar"]

You should return the indices: [0,9].  (order does not matter).

 

 

        思路：本题本质上与《Longest SubstringWithout Repeating Characters》是一样的。但是要注意几个地方：

”words”中的单词可能会重复；

left指针只能一步一步的走，不能跨越，比如这样的字符串s和words：

s: abcdefghidef

words: [“abc”, ”bcd”, ”cde”, ”def”, “ghi”]

 

        本题还是需要使用hash表来快速判断是否找到了words中的单词，注意hash表中还需要记录该单词出现的次数。

如果没找到，则left++,如果找到了，但是找到的单词的次数已经超过了words中的次数，同样的left++。代码如下：

typedef struct hashnode{char *str;int nums;struct hashnode *next;}HashNode;#define NHASH 31#define MULT 31unsigned int hash(char *p){    unsigned int h = 0;    for (; *p; p++)        h = MULT *h + *p;    return h % NHASH;}int isfindword(char *word, HashNode **wordhash, int hashlen){int hashvalue = hash(word);HashNode *ptr = wordhash[hashvalue];while(ptr != NULL){if(ptr->str == NULL)return 0;if(strcmp(ptr->str, word) == 0){return ptr->nums;}ptr = ptr->next;}return 0;}void  freehash(HashNode **wordhash, int hashsize){int i = 0; HashNode *ptr = NULL;HashNode *qtr = ptr;while(i < hashsize){ptr = wordhash[i];while(ptr != NULL){qtr = ptr;ptr = ptr->next;free(qtr->str);free(qtr);}wordhash[i] = NULL;i++;}    return;}int inserttohash(HashNode **map, char *word, int wordlen){int hashvalue = hash(word);HashNode *hp = map[hashvalue];HashNode *hq = hp;while(hp != NULL){if(strcmp(hp->str, word) == 0){hp->nums += 1;break;}else{hq = hp;hp = hp->next;}}if(hp == NULL){hp = calloc(1, sizeof(HashNode));hp->str = calloc(wordlen+1, sizeof(char));memcpy(hp->str, word, wordlen);hp->nums= 1;if(map[hashvalue] == NULL)map[hashvalue] = hp;elsehq->next = hp;}return hp->nums;}int* findSubstring(char* s, char** words, int wordsSize, int* returnSize){int hashlen = NHASH;HashNode **constwordhash = calloc(hashlen, sizeof(HashNode *));HashNode **acthash = calloc(hashlen, sizeof(HashNode *));int i;int hashvalue;int wordlen = strlen(words[0]);for(i = 0; i < wordsSize; i++){inserttohash(constwordhash, words[i], wordlen);}int findnums = 0;int getindexres = -1;int *res = calloc(strlen(s), sizeof(int));int resindex = 0;int left = 0;i = left;int forcounts = 0;int tstrlen = strlen(s);while(i < tstrlen && left <= tstrlen-wordsSize*wordlen){forcounts++;char *word = calloc(wordlen+1, sizeof(char));memcpy(word, s+i, wordlen);getindexres = isfindword(word, constwordhash, hashlen);if(getindexres == 0 || getindexres < inserttohash(acthash, word, wordlen)){findnums = 0;left++;i = left;freehash(acthash, hashlen);free(word);continue;}else{free(word);findnums++;if(findnums == wordsSize){res[resindex++] = left;findnums = 0;left++;i = left;freehash(acthash, hashlen); continue;}i += wordlen;}}*returnSize = resindex;freehash(constwordhash, hashlen);freehash(acthash, hashlen);free(constwordhash);free(acthash); return res;}